x^2+y^2=1(1)
y^2+z^2=5(2)
z^2+x^2=4(3)
[(1)+(2)+(3)]/2
x^2+y^2+z^2=5 (4)
(4)-(1)
z^2=4z=2或z=-2
(4)-(2)
x^2=0x=0
(4)-(3)
y^2=1y=1或y=-1
方程的解有以下4组：
x=0y=1z=2
x=0y=-1 z=2
x=0y=1z=-2
x=0y=-1z=-2